#register{
  height: 100%;
}

#register .register-box{
  position: absolute;
  left: 50%;
  top: 50%;
  width: 100%;
  transform: translate(-50%,-50%);
}

#register .next{
  position: relative;
  left: 50%;
  transform: translate(-50%);
  margin-top: 30px;
}